1. Field of the Invention
The field of this invention lies within the printer art. More particularly, it lies within the art of dot matrix printing wherein numerous dots are printed on a print media such as a sheet of paper to provide for an alpha numeric representation thereon. It specifically relates to the field wherein line printers are driven for movement across a print media in order to impress a number of dots thereon as the printer moves reciprocally across the print media.
2. Prior Art and Improvements
The prior art with regard to dot matrix printers encompasses multiple printers of various configurations. Such configurations use various wheels and hammers of various types to impress a dot on a print media. One particular type of printer which is known in the art is a line printer.
Line printers generally have a series of hammers. The series of hammers are implaced on a hammerbank which reciprocally moves across a print media. The print media is advanced across the hammers and is printed thereon by an inked ribbon.
Such hammers are supported on a hammerbank. The hammers are often held in place by a permanent magnet until released or fired. The release or firing takes place by the permanent magnetism holding the print hammers being overcome. The permanent magnetism is overcome by means of coils which receive a drive current to overcome the magnetism of the permanent magnets.
The foregoing action releases the hammers at a given time and causes them to move toward a print ribbon moving across their face. When the print ribbon is impressed by the hammers, it moves against an underlying print media which has the dots printed thereon. The hammers are released and controlled by electronic drivers which cause the coils to function.
The drivers are provided with logic consistent with the particular configuration of the print to be impressed on the print media. The logic can be in the form of local logic control in conjunction with a host and a central and data processing, unit integral to the printer.
In the past, it has been known to place a drive motor at an offset location from the hammers of a hammerbank and drive the hammerbank reciprocally by a crank or a connector. The movement is such wherein the crank or connector must move the hammerbank in a reciprocal manner in a sufficiently rapid manner so as to provide high speed printing. To help to accomplish this, a sufficiently strong and reliable connection is provided between the drive means such as the motor and the hammerbank. During reciprocal movement of the hammerbank, it moves in such a manner as to reciprocate and terminate this movement at various positions with regard to the desired effect on the print media. During its course of movement, when considering the mass of the hammerbank and the speed, it has been customary to counterbalance the hammerbank.
The foregoing counterbalances have been placed in a manner so that they can offset the movement of the hammerbank at different portions of its stroke or movement. Such offset relationships have not always been desirable because of the fact that they were offset and not in a compact and tightly oriented relationship to the hammerbank. In effect, the counterbalance although helping to balance the hammerbank was offset to a degree wherein it created forces which caused the printer to vibrate. Various methods have been used to dampen such vibrational forces. However, in most cases, the vibrational forces could only be dampened and not significantly offset in a consistent and balanced manner.
Another problem of the prior art is that the motor's flywheel was not always consistent and balanced with regard to a configuration to provide for smooth and compact mechanical movement. This creates a situation wherein the flywheel was not always such where it provided for a smooth balanced operation between the connecting rod and the hammerbank and counterbalance.
Another drawback of the prior art was that the capability of driving the hammerbank in a reciprocal manner was not accomplished to the extent where the various forces of movement could be readily dampened. In the alternative they could not be driven in such a manner so as to provide for integrated movement wherein one force offset the other as to the counterbalance and hammerbank and/or the connecting rods and the motor.
It is an object of this invention to overcome the problems of the prior art by having a flywheel which is integral to the motor. The motor is an inside out motor wherein the stator is on the inside. With the flywheel being on the outside, the inertia is enhanced to maintain the angular velocity of the motor and flywheel once it is up to speed and of course the mechanical elements connected thereto.
The integral motor is enhanced by a ferrite permanent magnet to enhance efficiency. The flywheel is a sintered metal flywheel having a high density without having to machine the flywheel. The permanent magnet is a sintered barium ferrite material with substantial qualities to enable the motor to function over a highly efficient range.
Another object of the invention and a most important consideration is the fact that the motor is directly connected to the connecting rods of the hammerbank and the counterbalance. This connection is through an integrated motor shaft connected to the flywheel. This relationship thereby transmits the inertia of the flywheel directly to the shaft and the connectors. The connectors are each connected to the respective portions of the integrated hammerbank and counterbalance for reciprocal movement thereof. This is accomplished by eccentrically driven connector rods that move 180.degree. degrees in opposite relationship with the eccentrics being formed as part of the motor shaft, and 180.degree. apart from each other.
Another object of the invention is to dynamically balance the system so that the flywheel, eccentrics, and connector rods are all dynamically balanced during their movement. This serves to minimize vibrations and unwanted forces throughout the cyclical movement of the printer.
A further and substantially important object of the invention is to provide for an integral hammerbank with an overlying and surrounding counterbalance. The relationship of the hammerbank and the counterbalance with its overlying relationship allows the structure to be compatibly and integrally balanced between the two respective members namely the hammerbank and the counterbalance. This overlying relationship causes a dynamically coordinated and balanced relationship to be established between them when connected to the connector rods. The invention further establishes close proximity of the hammerbank and counterbalance to the connector rods as an integral unit, for smoother operation. As can be appreciated the more distal an object is driven, the greater the forces are required and thereby greater dampening and other efforts must be undertaken to prevent unwanted forces to be applied to the dynamic system. This invention tends to eliminate such problems.
This invention provides for the integrated hammerbank and counterbalance to be connected with connector rods or drive rods which are in close proximity to each other. The rods drive a dynamically moving system comprised of the hammerbank and counterbalance. This is done in as close a proximity as practical with respect to the drive shaft emanating from the motor. This particular relationship enhances the dynamics so that less vibration and various forces are encountered. The result is to create a dynamically S balanced system driven by the motor and connecting rods as an entire integrally formed and balanced system.
For these reasons, the invention is a substantial step over the prior art and enhances line printer functions as well as smoothness of operation, speed of operation, and provides longevity and finer printing for a line printer than had previously been capable in the art.